Magnetically detented keyboard switch



Feb. 1, 1966 J. P. JONES, JR 3,233,061

MAGNETICALLY DETENTED KEYBOARD SWITCH Filed 001;. 5. 1964 mam-me REED sv mrcn BAR l I I CLOSURE s N COMPONENT l N0 CLOSURE I S COMPONENT m s '08 'H n V /YJ I [Y N 1 l/j I leA g L L EM 8 12a INVENTOR JOHN PAUL JONES, JR.

PC. BOARD United States Patent 3,233,061 MAGNETICALLY DETENTED KEYBOARD SWITCH John Paul Jones, Jr., Wynnewood, Pa., assignor to Navigation Computer Corporation, a corporation of Pennsylvania Filed Oct. 5, 1964, Ser. No. 401,485 7 Claims. (Cl. 200-87) This application deals generally with keyboard switches and in particular it deals with keyboard switches held in place by a magnetic detent in the manner afforded by my copending application Serial Number 175,942 filed February 27, 1962, for Magnetic Switch.

In the above-identified application, a magnet is attracted to a ferromagnetic panel in order to hold a push'button in normally detented position which can be overcome by application of manual pressure. This gives the keyboard switch a snapping or toggle-like action as a result of magnetic attraction to the panel. Such action is an ideal characteristic for applications in industrial environment or aboard ship where the keyboard is used intermittently and is desired to have a definite amount of resistance to vibration and accidental operation.

This version of a pushbutton assembly must be accompanied by some form of electrical switch for use in electrically operated control devices. While it is desirable to use the magnetic field afforded by the detent magnet of the pushbutton to operate a sealed-in-glass magnetic reed switch, this cannot be done in a straightforward manner. Thus, in a keyboard array, many magnets are positioned close to each other; and very little room remains for mounting switch assemblies. Since magnets are so closely spaced together many magnetic reed switches placed near. the keyboard would be subject to influence of the fields of various detent magnets. Furthermore, the strength of the magnetic field involved for operating as a detent is much too strong for normal use with a magnet reed-type switch.

Nevertheless, the switching characteristics of a reed relay switch are ideal for keyboard use since they are hermetically sealed to give long life, they have very low bounce characteristics upon closing which make them ideal to operate electronic switching circuits directly, and they will handle enough current, even if small in size, to enable them to operate solenoids and other high current devices directly.

Accordingly, it is an object of the invention to provide an improved keyboard switch utilizing a magnetic detent and a sealed-in-glass magnetic reed switch.

It is a further object of the invention to provide a magnetic key-operated glass reed switch capable of mounting very closely together within a grouping of magnets while being operable by a single magnetic key.

It is still another object of this invention to provide a keyboard assembly using magnetic pushbutton detents and incorporating glass reed-type switches within standard keyboard spacing dimensions and which may be mounted in a thin assembly adjacent the keyboard mounting panel by means of a printed circuit panel.

Thus, in accordance with the invention, the magnetic reed switch is operated upon a magnetic principle which permits use of a relatively strong magnet and yet gives a very sensitive switch characteristic operable over a very small portion of the motion of accompanying pushbutton to alford idealized keyboard switching characteristics. This is accomplished by providing in one switch position the axis of the magnetic reeds in the glass switch normal to the axis of the magnetic poles of a substantially cubic-shaped magnetic block located alongside the reed switch. Thus, the magnetic field is oriented in a direc- 3,233,061 Patented Feb. 1, 1966 "ice tion which does not effect closure of the reed contacts; and therefore, the magnetic field may be as strong as desired for detenting action while retaining the reed switch contacts in a normally open position. Operation of the reed switch is then obtained by a limited arcuate rotation of the magnetic field of the detent magnet block to give a vector flux component operating to close the magnetic reed switch contact. This gives a very sharp control of the closure position of the switch contacts with a small amount of motion of the pushbutton assembly, even when the magnetic field strength is so great that it would normally saturate the magnetic reeds and keep them in a close-d position while placed so closely to the reed switch contacts as required in a keyboard assembly.

Furthermore, this new principle of magnetic flux operation is highly desirable in the operation of a keyboard switch which should operate only once and not be subject to contact bounce upon opening which could introduce an erroneous signal. Thus, the field required to close the switch contacts is approximately six times greater than that required to hold the contacts closed. Thus, when the contacts close, they are held in closed position until the magnetic flux is rotated to a position at which it is unable to reclose the switches without considerable retracing of its movement before the switch is opened and the reed contacts are released. This removes possibility of contact bounce and makes it virtually impossible to provide a false closure as the key is released. Conversely, on the downward stroke, the magnetic detent produces a snap-action which assures that the field will not remain at a position just at the threshold of contact closure, so that a bounce on closure of the key is also virtually impossible. Thus, the construction of the present invention utilizes the characteristics of the magnet in corn bination with those of the reed switch in order to obtain idealized operational characteristics of a pushbutton assembly which therefore may be used directly into computer-type circuits and provide only a single closure each time the pushbutton is operated. In this manner, the magnetic switch assembly provides positive action over a very small region of manual motion of the pushbutton in closing and prevents contact bounce while using the characteristics of the detent magnet as well for providing a keyboard detenting feature.

In order to prevent operation of the magnetic reed switches by the fields of more than one of the closely spaced detenting magnets, when their fields normal to that of the ferromagnetic retaining panel are rotated by manual operation of the pushbutton, the switch is mounted between the sides of two adjacent magnets; and each of the magnets has a ferromagnetic field shorting bar mounted alongside one side to assure that the field entering the switch for operation thereof comes from the remaining single one of the two adjacent magnets.

Further features and objects of the invention will be discussed throughout the following specification with reference to the accompanying drawings, wherein:

FIGURE 1 is an exploded view, in perspective, of a keyboard assembly constructed in accordance with the principles of this invention;

FIGURES 2 and 3 are fragmentary views of a magnet and switch assembly illustrating the operation of the magnetic field with associated vector diagrams;

FIGURE 4 is a front elevation view, partly in section, of a keyboard assembly constructed in accordance with this invention; and

FIGURE 5 is a side view of a switch mounted on a keyboard panel in accordance with the provisions of the invention.

As may be seen from FIGURE 1, the pushbutton of key assembly comprises only two parts, namely, a key 19 of nonmagnetic material such as plastic and a block magnet 12 affixed to the shaft 19 of the key on the other side of an aperture 13 in a ferromagnetic mounting panel 11. The magnet 12 may be retained in the plastic key assembly 16 by means of a mounting screw 14. Alongside one edge of the magnetic block 12 is a reed switch 16 mounted on terminals 17. This is a conventional sealed-in-glass magnetic reed switch which extends closely to and adjacent one side of the magnet block with its field oriented with magnetic poles normal to the plane of the panel 11, as shown in FIGURE 2. Thus, the poles of the magnet and the magnetic axis S'N' of the reed switch are normal when the switch is placed parallel to the plane of panel 11'. alongside one edge of the magnetic block 12. In this way, the magnetic field does not affect the closure of the reed contacts which are held in normally opened position.

As may be seen best from FIGURE 5, when the key It is depressed the magnet 12 is removed from parallel contact with the top metal panel and is tilted through a limited are about one edge to attain the limiting down (or on) position at which the head of the plastic key 10 is in contact with the panel 11. Because of the detent action of the ferromagnet, when pushed it quickly snaps from one position to the other; and the magnetic attraction of the magnet 12 to the panel 11 offers resistance against accidental light bumping of the switch and makes it immune to harmonic vibrations as found aboard ship or on machinery which precludes use of spring-loaded keys, so that this key assembly is especially adaptable to any application near vibrating machinery on aircraft, shipboard and the like.

The simplicity of the switch in its mechanical movement is partly due to the arcuate motion of the magnet 12 afforded by the shaft 19 of the key as it extends through the mounting panel aperture 13. Thus, the field of the magnet '12 is rotated through a small are as a push button is depressed to attain a relative position with switch 16 as shown in FIGURE 3. In this position, the vector component of the field serves to close the reed switch contacts.

A special feature of this invention is the fact that the keyboard switch can be supplied in two versions, either a normally closed switch or a normally open switch. Thus, when the reed switch 16 is mounted as shown in the phantom position of FIGURE 5, it begins its initial operation with the vector field as shown in FIGURE 3, when the switch is in its magnetically detented up position; but in its downward position shown in FIGURE the magnetic block is parallel to the switch 16 in the manner shown in FIGURE 2, to thereby effect opening of the contacts. Thus the keyboard switch can be provided in either normally opened or normally closed position by merely modifying the mounting angle of the switch on the printed circuit board 18 by way of example of reversing the positions of the long and short printed circuit terminal studs 17 and 17'.

Thus an improved operation of the switch panel may be used for driving through long lines into inputs of logic level switching circuits. Thus keeps long lines normally at ground potential and immune to noise until the switch is open.

In a keyboard configuration as shown best by FIGURE 4, the magnets 12A. and 12B are mounted closely together. Thus it may be seen that the field shorting bars 15A and 15B are positioned alongside one of the edges of the corresponding magnetic blocks 12A and 12B to short out the field and leave only the field of one adjacent magnetic block 155 to operate the reed switch 16B, etc. The field shorting bar is simply a small angle bar 12 of soft ferromagnetic material extending alongside the entire edge of the block as may be seen from the perspective view of FIGURE 1 or in the on position of the switch as shown at 153 in FIGURE 4.

Therefore, in accordance with the present invention,

a new and improved keyboard is provided which utilizes detent magnets for the dual purpose of maintaining the push-button in normal detented position and operating a reed switch contact when the pushbutton is displaced manually from its normal position. This is accomplished in the novel manner of rotating the magnetic field of the detent magnetic block relative to the axis of a magnetic reed switch when operating the pushbutton. By use of a field shorting bar, such switches may be mounted side by side in a keyboard having standard spacing dimensions.

Therefore, having provided an improved keyboard and improved pushbutt-on switch assembly, those novel features believed representative of the invention are defined with particularity in the accompanying claims.

Having ascribed my invention, those novel features which are believed descriptive thereof are set forth with particularly in the following claims:

1. A keyboard switch assembly comprising in combination a ferromagnetic panel having side by side apertures therein to receive manually operable keys, keys afiixed in said apertures comprising a nonmagnetic pushbutton head on one side of said panel and a cubical magnet block affixed thereto on the other side of said panel to adhere thereto, said heads having an arcuate shaft extending through said apertures so that the magnet block rests in detented contact with said panel in one limiting key position and tilts about one edge to separate from said panel with the head in contact with said panel in the other limiting position, and a magnetic reed switch with an axial set of contacts positioned alongside said magnetic block at an angle permitting a change in its contact closure position responsive to a rotation of the magnetic field with respect to the axis of the contacts as said pushbutton is operated and said arcuate shaft extends through said aperture from said detented contact to said other limiting position.

2. An assembly as defined in claim 1 wherein the reed switch is mounted betwen two closely adjacent magnetic blocks in which the magnetic pole axis is normal to the plane of said panel, and including a ferromagnetic bar providing a closed flux path bet-ween the poles on one of the sides of the two magnet blocks adjacent to said reed switch.

3. An assembly as defined in claim 1 wherein the reed switch axis is mounted parallel to the panel and the magnet block has its magnetic axis normal to the plane of said panel, whereby the reed switch contacts are in a normally open position with the key in detented position.

An assembly as defined in claim 1 wherein the reed switch axis is mounted at an angle to the axis of the poles of the magnet block to thereby hold the contacts in a normally closed position when the key is in detented position.

5. A plurality of side by side keys extending through a ferromagnetic panel each comprising a nonmagnetic pushbutton on one side of the panel and a magnet detent block on the other side whereby a plurality of such blocks lie side by side, a magnetic reed switch mounted between adjacent magnet blocks, means rotating the axis of the field of one magnet block adjacent the switch with respect to the axis of the reeds in said switch as said pushbutton is depressed to thereby operate the switch, and a ferromganetic member shorting the magnetic field of the other magnet block adjacent the switch to prevent its influence on operation of the switch contacts.

6. A position-sensitive switch comprising in combination, a reed switch with magnetic reed contacts along a longitudinal axis, a magnetic block adjacent to said reed contacts and extending substantially the length thereof, and means for moving said block through a limited arcuate path to rotate the magnetic axis of the block with respect to the reed contact axis to thereby change the closure position of the contacts by influence of the ro- 5 tating magnetic field wherein the reed axis is normal to the magnetic axis in said detent position, to keep the switch contacts open.

7. A position-sensitive switch comprising in combina tion, a reed switch with magnetic reed contacts along a longitudinal axis, a magnetic block adjacent to said reed contacts and extending substantially the length thereof, means for moving said block through a limited arcnate path to rotate the magnetic axis of the block with respect to the reed contact axis to thereby change the closure position of the contacts by influence of the rotating magnetic field, wherein the magnet block has a ferromagnetic member holding it in a detent position with the reed axis at an angle to normal with the magnetic axis in said detent moving the block is limited to place the magnetic axis normal to said reed axis in its nondetented position, thereby opening said contacts.

BERNARD A. GILHEANY, Primary Examiner.

position to keep the switch contacts closed, and the means 15 J. J. BAKER, Assistant Examiner. 

1. A KEYBOARD SWITCH ASSEMBLY COMPRISING IN COMBINATION A FERROMAGNETIC PANEL HAVING SIDE BY SIDE APERTURES THEREIN TO RECEIVE MANUALLY OPERABLE KEYS, KEYS AFFIXED IN SAID APERTURES COMPRISING A NONMAGNETIC PUSHBUTTON HEAD ON ONE SIDE OF SAID PANEL AND A CUBICAL MAGNET BLOCK AFFIXED THERETO ON THE OTHER SIDE OF SAID PANEL TO ADHERE THERETO, SAID HEADS HAVING AN ARCUATE SHAFT EXTENDING THROUGH SAID APERTURES SO THAT THE MAGNET BLOCK RESTS IN DETENTED CONTACT WITH SAID PANEL IN ONE LIMITING KEY POSITION AND TILTS ABOUT ONE EDGE TO SEPARATE FROM SAID PANEL WITH THE HEAD IN CONTACT WITH SAID PANEL IN THE OTHER LIMITING POSITION, AND A MAGNETIC REED SWITCH WITH AN AXIAL SET OF CONTACTS POSITIONED ALONGSIDE SAID MAGNETIC BLOCK AT AN ANGLE PERMITTING A CHANGE IN ITS CONTACT CLOSURE POSITION RESPONSIVE TO A ROTATION OF THE MAGNETIC FIELD WITH RESPECT TO THE AXIS OF THE CONTACTS AS SAID PUSH- 